This invention relates to an apparatus and a process for curing and testing rubber.
Rheometers are known to the art of curing and testing rubber. As now known, a rheometer is a device for curing and testing rubber with a heated curing chamber into which raw uncured rubber samples are loaded to be transformed into the different, cured state. Within the heated curing chamber, a small ribbed rotor oscillates in contact with a loaded sample. A strain gauge senses torque upon the rotor caused by resistance of the rubber sample to rotor oscillation. Limit switches activate momentarily at each of the two extremes of rotor oscillation, to indicate the precise moments at which peak stress occurs. A recording device produces a graph of torque at peak stress versus time over the duration of a cure. A human operator observing the graph stops the cure by opening the rheometer and removing the sample. The operator stops the cure after the maximum torque at peak stress is reached and observed. Cure characteristics of the samples, including maximum torque at peak stress, are used for quality assurance of rubber batches from which the samples are taken, compounding error detection, and design of items made of the batches.
Known rheometers are each major investments in the art of rubber curing. As a result, the time taken for each cure and test with a rheometer is a critical factor in the successful commercial use of the rheometer. With rheometers as known, each cure and test must be continued through the time a maximum torque at peak stress is reached and observed. Further, the decision when to terminate a cure and test is undesirably left to the discretion of the operator, who can use only whatever judgment he has, based upon observation of the graph, that the maximum torque has been reached. The necessity of awaiting the achievement of maximum torque at peak stress, and the uncertainty in the decision to terminate the cure and test, results in increased times for cures and tests, and resultant loss of rheometer time for other cures and tests.